Abstract The dystonias are chronic, debilitating disorders. There are no cures, and the currently available treatments target only the symptoms and are only partly successful. Efforts to develop new treatments depend on the ability to measure the severity of the symptoms. Traditionally, severity is measured with human-scored instruments known as clinical rating scales. However, because these rating scales are inherently subjective, they exhibit variability from one rating to the next ? even for the same rater. This limits their ability to accurately capture severity and detect changes in severity over time. Advances in video processing software offer the possibility to supplement clinical rating scales with a partially automated means of quantifying symptoms objectively. Our preliminary tests of computerized, video-based systems with dystonia patient videos suggest they can quantify several clinically important features of the most common types of dystonia. Our long-term goal is to maximize how these approaches can aid in monitoring progression, assessing treatment response, and optimizing treatment for dystonia. In this project, we will develop and validate this approach to objectively measure the motor symptoms of three common forms of dystonia: cervical dystonia (CD), blepharospasm (BSP), and laryngeal dystonia (LD). For CD and BSP, the system uses advanced software known as the Computer Expression Recognition Toolbox (CERT) to measure various abnormal movements from video recordings of the patient?s face. CERT has been used extensively in neurologically normal populations and it is robust to highly variable video recording conditions. Although this type of approach has never before been applied to LD, we will develop a similar system to measure abnormal activity in the vocal cords captured on video during examination of the larynx. For each of the three forms of dystonia, our aims are to: a) test how well the system captures specific features of the dystonia, b) evaluate how combinations of those features relate to global clinical assessments of severity, c) compare the system?s assessment of severity with patient-reported assessments of quality of life, and d) determine whether the system can detect changes in severity associated with botulinum toxin injections, the most common treatment for these forms of focal dystonia. Upon completion, we will have developed and validated new methods to measure severity of the most common dystonias. The methods will be useful for both basic and clinical research in dystonia. Basic research in genetics, proteomics, and brain imaging, for example, relies on severity assessments for assigning patients to different groups and/or determining how aspects of the patient?s neurobiology relate to symptom severity. Clinical research on the natural progression of dystonia and its response to new treatments also relies on severity assessments. Thus this project will help amplify the impact of both basic and clinical research and help accelerate the development of new treatments for dystonia.